METHOD AND APPARATUS FOR VARIABLE FREQUENCY CATV JAMMING

METHODE ET APPAREIL DE BROUILLAGE A FREQUENCE VARIABLE POUR STAC

English Abstract

A method and apparatus for controlling the reception of selected
channels to individual subscribers in a CATV system, that involves
jamming each channel on a time divisional basis, to all of the
subscribers who are not entitled to receive the channel being jammed. A
frequency generating means, capable of generating a variety of
frequencies, generates an initial frequency that is similar in
amplitude to the amplitude of a typical television channel's carrier
wave frequency. That generated frequency is compared to a reference
frequency which would be suitable for jamming one of the channels to be
jammed. If the generated frequency is too high or too low, the
frequency generating means generates a new frequency which is,
respectively, either lower or higher than the initial frequency it
generated. If the new generated frequency is still higher or lower than
the reference frequency, the frequency generating means generates
another new frequency, which is respectively, either lower or higher than
the previous generated frequency, but by a lesser amount than the amount
by which the previous generated frequency differed from the frequency
generated before it. The generation of new frequencies continues until
one of them is within a desired range of the reference frequency, the
input to the frequency generating means which caused that frequency to be
generated is then stored in memory. The same procedure is used to obtain
memorized inputs to the frequency generating means for generating
frequencies to jam each channel to be controlled. The memorized inputs
are then sent on a time divisional basis to the frequency generating
means, and the resulting generated jamming frequencies are transmitted on
a time divisional basis to each of the subscribers who are not entitled
to receive the channel they are jamming. Then, in a cycle, after a
period of time, the jamming of channels is interrupted for a small period

of time during which the inputs to generate the jamming frequencies are
recalculated using the same calculation method, and re-memorized, then
the calculation process ceases and the jamming resumes.

French Abstract

L'invention est constituée par une méthode et un appareil servant à contrôler la réception de canaux sélectionnés par des abonnés particuliers d'un STAC qui brouillent les canaux au moyen d'une répartition temporelle pour tous les abonnés non autorisés à recevoir les canaux brouillés. Un générateur d'oscillations capable de produire des oscillations de fréquences diverses produit une oscillation initiale d'amplitude voisine de celle de la porteuse d'un signal de télévision typique. La fréquence de l'oscillation produite est comparée à une fréquence de référence qui serait appropriée pour brouiller l'un des canaux à brouiller. Si la fréquence de l'oscillation produite est trop élevée ou trop basse, le générateur d'oscillations produit une nouvelle oscillation dont la fréquence est inférieure ou supérieure à la fréquence de l'oscillation initiale. Si cette nouvelle fréquence est encore plus élevée ou plus basse que la fréquence de référence, le générateur d'oscillations produit encore une nouvelle oscillation dont la fréquence est inférieure ou supérieure à celle de l'oscillation précédente, mais d'un degré moindre que la différence entre la fréquence de l'oscillation précédente et celle de l'oscillation produite qui a précédé celle-ci. La production de nouvelles oscillations se poursuit jusqu'à ce que l'une d'elles ait une fréquence suffisamment rapprochée de la fréquence de référence; le signal d'entrée du générateur d'oscillations est alors stocké en mémoire. La même procédure est utilisée pour stocker en mémoire les signaux transmis au générateur d'oscillations qui produit des oscillations de fréquences appropriées pour brouiller chacun des canaux à contrôler. Les signaux mémorisés sont alors transmis en répartition temporelle au générateur d'oscillations et les signaux de brouillage produits sont transmis en répartition temporelle à chacun des abonnés non autorisés à recevoir les canaux brouillés. Après un certain intervalle de temps, le brouillage des canaux est interrompu durant un bref instant au cours d'un cycle dans lequel les signaux utilisés pour produire les oscillations de brouillage sont recalculés de la même façon et réintroduits en mémoire, puis le processus de calcul se termine et le brouillage reprend.

Claims

C L A I M S
The embodiments of the invention in which an exclusive property or
privilege is claimed are defined as follows:
1. A method for controlling the reception of selected television
channels by individual subscribers in a CATV system, which sslected
television channels are individually referred to as channel z, comprised
of the following steps:
(A) Selecting and generating a Reference Frequency ("RFz") for each of
the channels "z", which is stable in frequency, wherein RFz is a
suitable frequency to jam channel z;
(B) Using a generating means to generate a frequency the amplitude of
which is slightly greater than the amplitude of the frequency of
the carrier wave of a typical television signal;
(C) Sending a Frequency Generation Signal ("FGSa") to the generating
means, which causes the generating means to generate a jamming
frequency ("JFa") that is similar to the carrier wave frequency of
a typical television channel's signal, and of a slightly greater
amplitude;
(D) Comparing JFa to RFz, and if JFa is higher or lower than RFz,
sending a different FGSa, which is either lower in voltage or
higher in voltage, respectively, than the previous FGSa, by an
initial amount, to the generating means, causing it to generate a
new JFa, then again comparing JFa with RFz, and if JFa is higher
or lower than RFZ, sending a new FGSa, which is either lower in
voltge or higher in voltage, respectively, than the previous FGSa,
by less than the previous amount, to the generating means, causing

it to generate a new JFa, which is again compared to RFz, until
the last increase or decrease in the frequency of JFa was < I,
where "I" is a frequency value such that RFz + I would jam channel
z, if the amplitude of RFz + I was within the correct parameters;
(E) Remembering the last FGSa, as FGSz, wherein FGSz is the FGSa that
causes the generating means to generate a JFa that will jam
channel z, wherein the JFa that will jam channel z is called JFz;
(F) Continuing steps (C), (D), and (E), until there is remembered a
FGSz for each channel z, and then suspending steps (C), (D), and
(E);
(G) In continuous rotation, each for durations suitable for jamming
the horizontal synchronization signal, combining JFz with the
television channels signals being transmitted to subscribers who
are not entitled to receive the television signal which JFz is
jamming; and
(H) Where "T" is a number to be selected as desired and appropriate,
after every T minutes, suspending step (G) for a period long
enough for steps (E) to (F) to be repeated, repeating steps (E) to
(F), and then resuming step (G).
2. A method for controlling the reception of selected television
channels by individual subscribers in a CATV system, which selected
television channels are individually referred to as channel z, comprised
of the following steps:
(A) Selecting and generating a Reference Frequency ("RFz") for each of
the channels "z", which is stable in frequency amplitude, wherein
RFz is a suitable frequency to jam channel z;
(B) Using a generating means to generate a frequency the amplitude of
which is slightly greater than the amplitude of the frequency of
the carrier wave of a typical television signal;

(C) Sending a Frequency Generation Signal ("FGSa") to the
generating means, which causes the generating means to generate a
jamming frequency ("JFa") that is similar to the carrier wave
frequency of a typical television channel's signal, and of a
slightly greater amplitude;
(D) Comparing JFa to RFz, and if JFa is higher or lower than RFz,
sending a different FGSa, which is either lower in voltage or
higher in voltage, respectively, than the previous FGSa, by an
initial amount, to the generating means, causing it to generate a
new JFa, then again comparing JFa with RFz, and if JFa is higher
or lower than RFz, sending a new FGSa, which is either lower in
voltge or higher in voltage, respectively, than the previous FGSa,
by half of the previous amount, to the generating means, causing
it to generate a new JFa, which is again compared to RFz, until:
(i) the last increase or decrease in the frequency of JFa was < I,
where "I" is a frequency value such that RFz + I would jam channel
z, if the amplitude of RFz + I was within the correct parameters,
and (ii) the second last increase or decrease in the frequency of
JFa was < I, and (iii) the second last increase or decrease in the
frequency of JFa was the opposite of the last increase or decrease
in JFa;
(E) Remembering whichever of the last and second last FGSa's resulted
in JFa > RFz, as FGSz, wherein FGSz is the FGSa that causes the
generating means to generate a JFa that will jam channel z,
wherein the JFa that will jam channel z is called JFz;
(F) Continuing steps (D) and (E), until there is remembered a FGSz for
each channel z, and then suspending steps (D) and (E);
(G) In continuous rotation, each for durations suitable for jamming
the horizontal synchronization signal, combining JFz with the
television channels signals being transmitted to subscribers who

are not entitled to receive the television signal which JFz is
jamming; and
(H) Where "T" is a number to be selected as desired and appropriate,
after every T minutes, suspending step (G) for a period long
enough for steps (D) to (F) to be repeated, repeating steps (D) to
(F), and then resuming step (G).
3. A method for controlling the reception of selected television
channels by individual subscribers in a CATV system, which selected
television channels are individually referred to as channel z, as defined
in claims 1 or 2, which is further comprised of, during step (G), also
in continuous rotation, at predetermined intervals, each for durations
suitable for jamming the vertical synchronization signal, combining JFz
with the television channels signals being transmitted to subscribers who
are not entitled to receive the television signal which JFz is jamming.
4. A method for controlling the reception of selected television
channels by individual subscribers in a CATV system, which selected
television channels are individually referred to as channel z, as defined
in claims 1 or 2, wherein each JFz is stable in both frequency and
amplitude.
5. A method for controlling the reception of selected television
channels by individual subscribers in a CATV system, which selected
television channels are individually referred to as channel z, as defined
in claims 1 or 2, which is further comprised of, during step (G), also
in continuous rotation, at predetermined intervals, each for durations
suitable for jamming the vertical synchronization signal, combining JFz
with the television channels signals being transmitted to subscribers who
are not entitled to receive the television signal which JFz is jamming;

and wherein each JFz is stable in both frequency and amplitude.
6. A method for controlling the reception of selected television
channels by individual subscribers in a CATV system, which selected
television channels are individually referred to as channel z, as defined
in claims 1 or 2, wherein each JFz is stable in both frequency and
amplitude, and which is also comprised of, during step (G) periodically
varying the frequency of JFz within a range that will still allow each
JFz to be an effective jamming signal.
7. A method for controlling the reception of selected television
channels by individual subscribers in a CATV system, which selected
television channels are individually referred to as channel z, as defined
in claims 1 or 2, which is further comprised of, during step (G), also
in continuous rotation, at predetermined intervals, each for durations
suitable for jamming the vertical synchronization signal, combining JFz
with the television channels signals being transmitted to subscribers who
are not entitled to receive the television signal which JFz is jamming;
and also, during step (G) periodically varying the frequency of JFz
within a range that will still allow each JFz to be an effective jamming
signal.
8. A method for controlling the reception of selected television
channels by individual subscribers in a CATV system, which selected
television channels are individually referred to as channel z, as defined
in claims 1 or 2, wherein each JFz is stable in frequency, and which is
also comprised of during step (G) periodically varying the amplitude of
JFz within a range that will still allow each JFz to be an effective
jamming signal.

9. A method for controlling the reception of selected television
channels by individual subscribers in a CATV system, which selected
television channels are individually referred to as channel z, as defined
in claims 1 or 2, which is further comprised of, during step (G), also
in continuous rotation, at predetermined intervals, each for durations
suitable for jamming the vertical synchronization signal, combining JFz
with the television channels signals being transmitted to subscribers who
are not entitled to receive the television signal which JFz is jamming;
and also during step (G) periodically varying the amplitude of JFz within
a range that will still allow each JFz to be an effective jamming signal.
10. A method for controlling the reception of selected television
channels by individual subscribers in a CATV system, which selected
television channels are individually referred to as channel z, as defined
in claims 1 or 2, wherein each JFz is stable in frequency, and which is
also comprised of during step (G) periodically varying the frequency and
amplitude of JFz within ranges that will still allow each JFz to be an
effective jamming signal.
11. A method for controlling the reception of selected television
channels by individual subscribers in a CATV system, which selected
television channels are individually referred to as channel Z, as defined
in claims 1 or 2, which is further comprised of, during step (G), also
in continuous rotation, at predetermined intervals, each for durations
suitable for jamming the vertical synchronization signal, combining JFz
with the television channels signals being transmitted to subscribers who
are not entitled to receive the television signal which JFz is jamming;
and also, during step (G) periodically varying the frequency and
amplitude of JFz within ranges that will still allow each JFz to be an
effective jamming signal.

12. An apparatus for generating and controlling the application of,
where N is an integer greater than 1 and less than 13, N jamming signals to
individual subscribers' lines in a CATV system which is offering at least N
channels that are individually referred to as channel z, comprised of:
(A) A Voltage Controlled Oscillator ("VCO") for generating, one at a
time, a number of different frequencies, each of which is
generally referred to as ("JFa"), and each of which is similar to
the frequency of a typical television signal's carrier wave, but
of a slightly greater amplitude;
(B) A set of Subscriber Jamming Signal Switches, each of which
receives the JFa, and each of which will transmit the JFa to the
subscriber's line to which it is connected, when it is closed;
(C) A Reference Frequency Generating Means that generates a stable
reference frequency ("REF");
(D) A Comparison Means that receives the JFa, and that receives the
REF, and that can divide the JFa by a factor of "Dz", wherein Dz
is a factor such that when JFa/Dz = REF, JFa is a frequency
suitable for jamming channel z, and wherein the comparison means
can compare the REF to JFa/Dz, and determine if REF is greater
than or less than JFa/Dz, and which Comparison Means can output
the results of the comparison; and
(E) A service control center ("SCC") that receives information from
the CATV system on which subscribers are entitled to receive which
television signals; and which outputs a Frequency Generating
Signal ("FGSa") to the VCO, that determines the frequency of JFa,
and which, based on the information it receives from the CATV
system, as to the frequencies of the carrier waves of each of
channels z, determines the value of Dz that the Comparison Means
must divide JFa by, so that if JFa/Dz = REF, JFa will be the
appropriate frequency for jamming the television signal of channel

z, and which starts the system by beginning step "Test" by sending
a FGSa to the VCO, causing it to generate JFa, and then sending
the appropriate information on the value of Dz, to the Comparison
Means, and then receiving from the Comparison Means, a first
signal if the comparison resulted in JFa/Dz > REF, and a second
signal if the comparison resulted in JFa/Dz < REF, and if JFa/Dz
is higher or lower than REF, sending a different FGSa, which is
either lower in voltage or higher in voltage, respectively, than
the previous FGSa, by an initial amount, to the VCO, causing it to
generate a different JFa, then, when the SCC receives the result
of the new comparison from the Comparison Means, if JFa/Dz is
higher or lower than REF, again sending a different FGSa, which is
either lower in voltge or higher in voltage, respectively, than
the previous FGSa, by less than the previous increase or decrease,
to the VCO, then again receiving the results of the comparison of
JFa/D to REF, and continuing to receive the results of the
comparison and to send out different FGSa's, until the last
increase or decrease in the frequency of JFa was < I, where"I" is
a pre-determined frequency value such that (REF x Dz) + I is a
correct frequency to jam channel z), and then the SCC stores the
last FGSa, as FGSz, wherein FGSz is the FGSz that causes the
generating means to generate a JFa that will jam channel z,
wherein the JFa that will jam channel z is called JFZ, and the SCC
continues the above series of operations until there is stored a
FGSz for each of the channels to be jammed, once all of the FGSz's
have been stored step Test is ended, then the SCC suspends the
operations of step Test and begins step Jam by sending, in
continuous rotation, each for durations of approximately 6 to 10
µS, each of the FGSz's to the VCO, and closing each of the
Subscriber Jamming Signal Switches to the subscribers'lines who

are not entitled to receive the television signal of channel z,
when JFz is being generated by the VCO, and opening the Jamming
Signal Switches of those subscribers who are entitled to receive
channel z, then, after a pre-determined period of time the SCC
suspends step Jam for a period of time long enough for step Test
to be performed, and again performs step Test, and then again
suspends step Test and again resumes step Jam, and continues to
alternate between steps Test and Jam, at predetermined periods of
time.
13. An apparatus for generating and controlling the application of,
where N is an integer greater than 1 and less than 13, N jamming signals to
individual subscribers' lines in a CATV system which is offering at least N
channels that are individually referred to as channel z, comprised of:
(A) A Voltage Controlled Oscillator ("VCO") for generating, one at a
time, a number of different frequencies, each of which is
generally referred to as ("JFa"), and each of which is similar to
the frequency of a typical television signal's carrier wave, but
of a slightly greater amplitude;
(B) A set of Subscriber Jamming Signal Switches, each of which
receives the JFa, and each of which will transmit the JFa to the
subscriber's line to which it is connected, when it is closed;
(C) A Reference Frequency Generating Means that generates a reference
frequency ("REF"), which is stable in frequency;
(D) A Comparison Means that receives the JFa, and that receives the
REF, and that can divide the JFa by a factor of "Dz", wherein Dz
is a factor such that when JFa/Dz = REF, JFa is a frequency
suitable for jamming channel z, and wherein the comparison means
can compare the REF to JFa/Dz, and determine if REF is greater
than or less than JFa/Dz, and which Comparison Means can output

the results of the comparison; and
(E) A service control center ("SCC") that receives information from
the CATV system on which subscribers are entitled to receive which
television signals; and which outputs a Frequency Generating
Signal ("FGSa") to the VCO, that determines the frequency of JFa,
and which, based on the information it receives from the CATV
system, as to the frequencies of the carrier waves of each of
channels z, determines the value of Dz that the Comparison Means
must divide JFa by, so that if JFa/Dz = REF, JFa will be the
appropriate frequency for jamming the television signal of channel
z, and which starts the system by beginning step "Test" by sending
a FGSa to the VCO, causing it to generate JFa, and then sending
the appropriate information on the value of Dz, to the Comparison
Means, and then receiving from the Comparison Means, a first
signal if the comparison resulted in JFa/Dz > REF, and a second
signal if the comparison resulted in JFa/Dz < REF, and if JFa/Dz
is higher or lower than REF, sending a different FGSa, which is
either lower in voltage or higher in voltage, respectively, than
the previous FGSa, by an initial amount, to the VCO, causing it to
generate a different JFa, then, when the SCC receives the result
of the new comparison from the Comparison Means, if JFa/Dz is
higher or lower than REF, again sending a different FGSa, which is
either lower in voltage or higher in voltage, respectively, than
the previous FGSa, by half of the previous increase or decrease,
to the VCO, then again receiving the results of the comparison of
JFa/D to REF, and continuing to receive the results of the
comparison and to send out different FGSa's, until: (i) the last
increase or decrease in the frequency of JFa was < I, where "I"
is a pre-determined, fixed, frequency value such that (REF x Dz)
+ I is a correct frequency to jam channel z), and (ii) the second

last increase or decrease in the frequency of JFa was < I, and
(iii) the second last increase or decrease in the frequency of
JFa was the opposite of the last increase or decrease in JFa,
then the SCC stores whichever of the last and second last FGSa's
resulted in JFa/Dz > REF, as FGSz, wherein FGSz is the FGSz that
causes the generating means to generate a JFa that will jam
channel z, wherein the JFa that will jam channel z is called JFz,
and the SCC continues the above series of operations until there
is stored a FGSz for each of the channels to be jammed, once all
of the FGSz's have been stored step Test is ended, then the SCC
suspends the operations of step Test and begins step Jam by
sending, in continuous rotation, each for durations of
approximately 6 to 10 µS, each of the FGSz's to the VCO, and
closing each of the Subscriber Jamming Signal Switches to the
subscribers'lines who are not entitled to receive the television
signal of channel z, when JFz is being generated by the VCO, and
opening the Jamming Signal Switches of those subscribers who are
entitled to receive channel z, then, after a pre-determined period
of time the SCC suspends step Jam for a period of time long enough
for step Test to be performed, and again performs step Test, and
then again suspends step Test and again resumes step Jam, and
continues to alternate between steps Test and Jam, at
predetermined periods of time.
14. An apparatus for generating and controlling the application of,
where N is an integer greater than 1 and less than 13, N jamming signals to
individual subscribers' lines in a CATV system which is offering at least N
channels that are individually referred to as channel z, as defined in
claims 12 or 13, wherein the SCC additionally, during step Jam, sends out,
in continuous rotation, every 15 to 20 mS/N, each for durations of

approximately 150 to 300 /µS, each of the FGSz's to the VCO, and closes each
of the Subscriber Jamming Signal Switches to the subscribers' lines who are
not entitled to receive the television signal of channel z, when JFz is
being generated by the VCO, and opens the Jamming Signal Switches of those
subscribers who are entitled to receive channel z.
15. An apparatus for generating and controlling the application of,
where N is an integer greater than 1 and less than 13, N jamming signals to
individual subscribers' lines in a CATV system which is offering at least N
channels that are individually referred to as channel z, as defined in
claims 12 or 13, wherein the SCC additionally, during step Jam, sends out,
in continuous rotation, every 15 to 20 mS/N, each for durations of
approximately 150 to 300 µS, each of the FGSz's to the VCO, and closing
each of the Subscriber Jamming Signal Switches to the subscribers' lines
who are not entitled to receive the television signal of channel z, when
JFz is being generated by the VCO, and opening the Jamming Signal Switches
of those subscribers who are entitled to receive channel z, and wherein the
SCC, also during step Jam, periodically varies FGSz so that each JFz's
frequency varies within acceptable limits a predetermined number of times
per second.
16. A method for controlling the reception of, where N is an integer
greater than 1 and less than 13, N selected television channels by
individual subscribers in a CATV system, which channels are individually
referred to as channel z, comprised of:
(A) Generating a Reference Frequency ("REF");
(B) Sending an initial Frequency Generation Signal ("FGSa") to a
generating means, which causes the generating means to generate a
jamming frequency ("JFa") that is stable in frequency and of a
slightly greater amplitude than the amplitude of the carrier wave

of a typical television signal;
(C) Dividing JFa by "Dz", where Dz is a factor such that JFa will have
a frequency suitable for jamming channel z when JFa/Dz = REF, and
then comparing JFa/Dz to REF, and if JFa/Dz is higher or lower in
frequency than REF sending a different FGSa, which is either lower
in voltage or higher in voltage, respectively, than the previous
FGSa, by an initial amount, to the generating means, causing it to
generate a new JFa, then again comparing the generated JFa,
divided by Dz, with REF, and if JFa/Dz is higher or lower than
REF, sending a new FGSa, which is either lower in voltage or
higher in voltage, respectively, than the previous FGSa, by less
than the previous amount, to the generating means, causing it to
generate a new JFa, which, divided by Dz, is again compared to
REF, until the last increase or decrease in the frequency of JFa
was < I, where I is a frequency value such that if JFa would jam
channel z, then JFa + I would jam channel z, and then storing the
last FGSa, as FGSz, wherein FGSz is the FGSa that causes the
generating means to generate a JFa that will jam channel z, which
JFa is called JFz;
(D) Continuing steps (B) and (C) until there is a stored FGSz for each
channel z, and then suspending steps (B) and (C);
(E) After step (D), in continuous rotation, each for durations of
approximately 6 to 10 µS, combining JFz with the television
channels signals being transmitted to subscribers who are not
entitled to receive the television signal which JFz is jamming;
and
(F) After each period of T minutes suspending step (E) for a period of
time for a period long enough for steps (B), (C), and (D) to be
performed, performing said steps, and then resuming step (E).

17. A method for controlling the reception of, where N is an integer
greater than 1 and less than 13, N selected television channels by
individual subscribers in a CATV system, which channels are individually
referred to as channel z, comprised of:
(A) Generating a Reference Frequency ("REF");
(B) Sending a Frequency Generation Signal ("FGSa") to a generating
means, which causes the generating means to generate a jamming
frequency ("JFa") that is stable in frequency and of a slightly
greater amplitude than the amplitude of the carrier wave of a
typical television signal;
(C) Dividing JFa by "Dz", where Dz is a factor such that JFa will have
a frequency suitable for jamming channel z when JFa/Dz = REF, and
then comparing JFa/Dz to REF, and if JFa/Dz is higher or lower in
frequency than REF sending a different FGSa, which is either lower
in voltage or higher in voltage, respectively, than the previous
FGSa, by an initial amount, to the generating means, causing it to
generate a new JFa, then again comparing the generated JFa,
divided by Dz, with REF, and if JFa/Dz is higher or lower than
REF, sending a new FGSa, which is either lower in voltage or
higher in voltage, respectively, than the previous FGSa, by half
of the previous amount, to the generating means, causing it to
generate a new JFa, which, divided by Dz, is again compared to
REF, until: (a) the last increase or decrease in the frequency of
JFa was < I, where I is a frequency value such that if JFa would
jam channel z, then JFa + I would jam channel z, and (b) the
second last increase or decrease in the frequency of JFa was < I,
and (c) the second last increase or decrease in the frequency of
JFa was the opposite of the last increase or decrease in JFa,
then storing whichever of the last and second last FGSa's resulted
in JFa/Dz > REF, as FGSz, wherein FGSz is the FGSa that causes

the generating means to generate a JFa that will jam channel z,
which JFa is called JFz;
(D) Continuing step (C) until there is a stored FGSz for each channel
z, and then suspending step (C);
(E) After step (D), in continuous rotation, each for durations of
approximately 6 to 10 µS, combining JFz with the television
channels signals being transmitted to subscribers who are not
entitled to receive the television signal which JFz is jamming;
and
(F) After each period of T minutes suspending step (E) for a period of
time for a period long enough for steps (C) and (D) to be
performed, performing said steps, and then resuming step (E).
18. A method for controlling the reception of, where N is an integer
greater than 1 and less than 13, N selected television channels by
individual subscribers in a CATV system, which channels are individually
referred to as channel z, as defined in claims 16 or 17, which is further
comprised of, during step (E), also in continuous rotation, once every 15
to 20 mS/N, each for periods of approximately 150 to 300 µS, combining JFz
with the television channels signals being transmitted to subscribers who
are not entitled to receive the television signal which JFz is jamming.
19. A method for controlling the reception of, where N is an integer
greater than 1 and less than 13, N selected television channels by
individual subscribers in a CATV system, which channels are individually
referred to as channel z, as defined in claims 16 or 17, which is further
comprised of, during step (E), also in continuous rotation, once every 15
to 20 mS/N, each for durations of approximately 150 to 300 µS, combining
JFz with the television channels signals being transmitted to subscribers
who are not entitled to receive the television signal which JFz is jamming,

and also during step (E) periodically varying the frequency of JFz within a
range that will still allow each JFz to be an effective jamming signal.
20. A method for controlling the reception of, where N is an integer
greater than 1 and less than 13, N selected television channels by
individual subscribers in a CATV system, which channels are individually
referred to as channel z, as defined in claims 16 or 17, which is further
comprised of, during step (E), also in continuous rotation, once every 15
to 20 mS/N, each for durations of approximately 150 to 300 µS, combining
JFz with the television channels signals being transmitted to subscribers
who are not entitled to receive the television signal which JFz is jamming,
and also during step (E), periodically varying the amplitude of JFz within
a range that will still allow each JFz to be an effective jamming signal.
21. A method for controlling the reception of, where N is an integer
greater than 1 and less than 13, N selected television channels by
individual subscribers in a CATV system, which channels are individually
referred to as channel z, as defined in claims 16 or 17, which is further
comprised of, during step (E), also in continuous rotation, once every 15
to 20 mS/N, each for durations of approximately 150 to 300 µS, combining
JFz with the television channels signals being transmitted to subscribers
who are not entitled to receive the television signal which JFz is jamming,
and also during step (E), periodically varying the frequency and amplitude
of JFz within ranges that will still allow each JFz to be an effective
jamming signal.
22. A method for controlling the reception of, where N is an integer
greater than l and less than 13, N selected television channels by
individual subscribers in a CATV system, which channels are individually
referred to as channel z, as defined in claims 16 or 17, which is further

comprised of, during step (E), also in continuous rotation, once every 15
to 20 mS/N, each for durations of approximately 150 to 300 µS, combining
JFz with the television channels signals being transmitted to subscribers
who are not entitled to receive the television signal which JFz is jamming,
and also during step (E), periodically varying the frequency and amplitude
of JFz within ranges that will still allow each JFz to be an effective
jamming signal, and wherein N = 12.
23. An apparatus for generating and controlling the application of 12
jamming signals to individual subscribers' lines in a CATV system which
is offering at least 12 channels that are individually referred to as
channel z, comprised of:
(A) A Voltage Controlled Oscillator ("VCO") for generating, one at a
time, a number of different frequencies, each of which is
generally referred to as ("JFa") and each of which is of a
slightly greater amplitude than the carrier wave frequency of the
signal of a typical television signal;
(B) A set of Subscriber Jamming Signal Switches, each of which
receives the JFa, and each of which will transmit the JFa to the
subscriber's line to which it is connected, when it is closed;
(C) A Quartz Crystal Reference Frequency Generating Means that
generates a reference frequency ("REF"), which is stable
in frequency;
(D) A Frequency Comparator Circuit ("FCC") that receives the JFa and
that receives the REF and can divide the JFa by a factor of "Dz",
wherein if JFa/Dz = REF, then JFa is a correct frequency to jam
the horizontal synchronization signal of channel z, and which FCC
can compare the JFa/Dz to REF and determine if one is greater than
the other;
(E) A Integrator that receives result from the FCC and averages it to

produce a first signal if JFa/Dz > REF, and produces a second
signal if JFa/Dz < REF;
(F) A Digital to Analog Converter ("DAC") which outputs, one at a
time, a variety of different analog voltages, in response to
digital signals that are inputted to it; and
(G) A Service Control Center ("SCC") that receives information from
the CATV system on which subscribers are entitled to receive which
television signals; and which begins step "Test" by outputing a
Digital Code that represents a Signal ("DCSa") to the DAC, which
converts it into an analog Frequency Generating Signal ("FGSa")
which it sends to the VCO, resulting in the VCO outputting a JFa,
then the SCC, based on the information it receives from the head
end as to the frequencies of the channels to be jammed, determines
the value of Dz, the SCC then sends the information of what value
Dz should be to the FCC, the SCC then receives a first signal from
the Integrator if the comparison in the FCC resulted in JFa/Dz >
REF, and a second signal if the comparison resulted in JFa/Dz <
REF, respectively, if JFa/Dz is higher or lower than REF, the SCC
sends a different DCSa, which will result in a JFa that is either
lower in frequency or higher in frequency, than the previous JFa,
by an initial amount, then when the SCC receives the result of the
new comparison, respectively, if JFa/Dz is higher or lower than
REF, the SOC sends a different DCSa, which will result in a JFa
that is either lower in frequency or higher in frequency, than the
previous JFa, by less than the previous increase or decrease,
until the last increase or decrease in the frequency of JFa was <
I, where "I" is a pre-determined, fixed, frequency value, such
that if JFz would be a correct frequency to jam channel z, JFa + I
would also be a correct frequency to jam channel z, at which time
the SCC stores the last DCSa, as DCSz, wherein DCSz is the DCSa

that results in the VCO generating a JFa that will jam channel z,
wherein the JFa that will jam channel z is called JFz, the SCC
continues to operate as stated until there is a stored DCSz for
each of the channels to be jammed, then the SCC suspends the
operations of step Test and begins step Jam by sending, in
continuous rotation, each for durations of between approximately
6 and 10 µS, each of the DCSz's to the VCO, and closing each of
the Subscriber Jamming Signal Switches to the subscribers who are
not entitled to receive the television signal of channel z, when
DCSz is being sent to the VCO,and opening the Jamming Signal
Switches of those subscribers who are entitled to receive channel
z, when DCSz is being sent to the VCO, then after a pre-determined
period of time T1 the SCC suspends step Jam for a period of time
T2, which is long enough for step Test to be performed, and the
SCC again performs step Test, and then the SCC again suspends step
Test for a period of time T1, and again resumes step Jam for
period T2, and continues to alternate between steps Test and Jam,
during periods T2 and T1, respectively.
24. An apparatus for generating and controlling the application of 12
jamming signals to individual subscribers' lines in a CATV system which
is offering at least 12 channels that are individually referred to as
channel z, comprised of:
(A) A Voltage Controlled Oscillator ("VCO") for generating, one at a
time, a number of different frequencies, each of which is
generally referred to as ("JFa") and each of which is of a
slightly greater amplitude than the carrier wave frequency of the
signal of a typical television signal;
(B) A set of Subscriber Jamming Signal Switches, each of which
receives the JFa, and each of which will transmit the JFa to the

subscriber's line to which it is connected, when it is closed;
(C) A Quartz Crystal Reference Frequency Generating Means that
generates a reference frequency ("REF"), which is stable
in frequency;
(D) A Frequency Comparator Circuit ("FCC") that receives the JFa and
that receives the REF and can divide the JFa by a factor of "Dz",
wherein if JFa/Dz =REF, then JFa is a correct frequency to jam the
horizontal synchronization signal of channel z, and which FCC can
compare the JFa/Dz to REF and determine if one is greater than the
other;
(E) A Integrator that receives result from the FCC and averages it to
produce a first signal if JFa/Dz > REF, and produces a second
signal if JFa/Dz < REF;
(F) A Digital to Analog Converter ("DAC") which outputs, one at a
time, a variety of different analog voltages, in response to
digital signals that are inputted to it; and
(G) A Service Control Center ("SCC") that receives information from
the CATV system on which subscribers are entitled to receive which
television signals; and which begins step "Test" by outputing a
Digital Code that represents a Signal ("DCSa") to the DAC, which
converts it into an analog Frequency Generating Signal ("FGSa")
which it sends to the VCO, resulting in the VCO outputting a JFa,
then the SCC, based on the information it receives from the head
end as to the frequencies of the channels to be jammed, determines
the value of Dz, the SCC then sends the information of what value
Dz should be to the FCC, the SCC then receives a first signal from
the Integrator if the comparison in the FCC resulted in JFa/Dz >
REF, and a second signal if the comparison resulted in JFa/Dz <
REF, respectively, if JFa/Dz is higher or lower than REF, the SCC
sends a different DCSa, which will result in a JFa that is either

lower in frequency or higher in frequency, than the previous JFa,
by an initial amount, then when the SCC receives the result of the
new comparison, respectively, if JFa/Dz is higher or lower than
REF, the SCC sends a different DCSa, which will result in a JFa
that is either lower in frequency or higher in frequency, than the
previous JFa, by half of the previous increase or decrease, until:
(a) the last increase or decrease in the frequency of JFa was < I,
where "I" is a pre-determined, fixed, frequency value, such that
if JFz would be a correct frequency to jam channel z, JFa + I
would also be a correct frequency to jam channel z; and (b) the
second last increase or decrease in the frequency of JFa was < I,
and (c) the second last increase or decrease in the frequency of
JFa was the opposite of the last increase or decrease in JFa, at
which time the SCC stores whichever of the last and second last
DCSa's resulted in JFa/Dz > REF, as DCSz, wherein DCSz is the
DCSa that results in the VCO generating a JFa that will jam
channel z, wherein the JFa that will jam channel z is called JFz,
the SCC continues to operate as stated until there is a stored
DCSz for each of the channels to be jammed, then the SCC suspends
the operations of step Test and begins step Jam by sending, in
continuous rotation, each for durations of between approximately
6 and 10 µS, each of the DCSz's to the VCO, and closing each of
the Subscriber Jamming Signal Switches to the subscribers who are
not entitled to receive the television signal of channel z, when
DCSz is being sent to the VCO, and opening the Jamming Signal
Switches of those subscribers who are entitled to receive channel
z, when DCSz is being sent to the VCO, then after a pre-determined
period of time T1 the SCC suspends step Jam for a period of time
T2, which is long enough for step Test to be performed, and the
SCC again performs step Test, and then the SCC again suspends step

Test for a period of time T1, and again resumes step Jam for
period T2, and continues to alternate between steps Test and Jam,
during periods T2 and T1, respectively.
25. An apparatus for generating and controlling the application of 12
jamming signals to individual subscribers' lines in a CATV system which
is offering at least 12 channels that are individually referred to as
channel z, as defined in claims 23 or 24, wherein the SCC additionally,
during step Jam, sends, approximately once every 1.21 to 1.66mS, in
continuous rotation, 0.15 to 0.30 mS long pulses of each of the DCSz's to
the VCO, and closes each of the Subscriber Jamming Signal Switches to the
subscribers who are not entitled to receive the television signal of
channel z, when DCSz is being sent to the VCO, and opens the Jamming Signal
Switches of those subscribers who are entitled to receive channel z, when
DCSz is being sent to the VCO.
26. An apparatus for generating and controlling the application of 12
jamming signals to individual subscribers' lines in a CATV system which
is offering at least 12 channels that are individually referred to as
channel z, as defined in claims 23 or 24, wherein the SCC additionally,
during step Jam, sends, approximately once every 1.21 to 1,66 mS, in
continuous rotation, 0.15 to 0.30 mS long pulses of each of the DCSz's to
the VCO, and closes each of the Subscriber Jamming Signal Switches to the
subscribers who are not entitled to receive the television signal of
channel z, when DCSz is being sent to the VCO, and opens the Jamming Signal
Switches of those subscribers who are entitled to receive channel z, when
DCSz is being sent to the VCO, and wherein the SCC also, during step Jam,
varies the digital code it sends out as DCSz, so that the frequency of JFz
varies slightly a predetermined number of times per second.

27. An apparatus for generating and controlling the application of 12
jamming signals to individual subscribers' lines in a CATV system which
is offering at least 12 channels that are individually referred to as
channel z, as defined in claims 23 or 24, which is further comprised of:
(H) A Buffer that receives the JFz from the VCO;
(I) A Master Switch that receives the JFz from the Buffer;
(J) A Variable Attenuator that receives the JFz from the Master
Switch;
(K) A Low Pass Filter that eleminates harmonics, which receives JFz
from the Master Switch, and which eliminates any harmonics in JFz;
(L) wherein the JFz generated by the VCO is outputted to the Buffer,
then to the Master Switch, then to the Variable Attenuator, then
to the Low Pass Filter, and from the Low Pass Filter to the
Subscriber Jamming Signal Switches; and
(M) wherein the SCC additionally, during step Jam, sends,
approximately once every 1.21 to 1.66mS, in continuous rotation,
0.15 to 0.30 mS long pulses of each of the DCSz's to the VCO, and
closes each of the Subscriber Jamming Signal Switches to the
subscribers who are not entitled to receive the television signal
of channel z, when DCSz is being sent to the VCO, and opens the
Jamming Signal Switches of those subscribers who are entitled to
receive channel z, when DCSz is being sent to the VCO, and wherein
the SCC also, during step Jam, varies the digital code it sends
out as DCSz, so that the frequency of JFz varies slightly a
predetermined number of times per second, and wherein the SCC
also, during step Jam, varies the signal it sends to the Variable
Attenuator, so that the Variable Attenuator slightly varies the
amplitude of JFz a predetermined number of times per second to
achieve an even more effective jamming.

Description

2 ~
D~c-lO.~u~
V~ Rr~ FREQUENCY CATY JAH~ING ~IETHOD AND APPARATUS
~ackground of the Invent~on
Fleld of the Inve~ n:
me inventlon relates to QTV systems, and more particularly to a
method and a~aLa~ for selectlvely ~amming selected channels to
~elected subscrlber~ ln a CATV system.
Descriptlon of Related Art:
QTV systems commonly provlde a multiple of ch~nn~l~ to their
subscrlbers; such systems are well known in the art and have been for
many years. Many CATV systems, however, do not require each of their
sub~crlbers to subscribe to every one of the channels they offer. The
result is that an effective method, and a~d-d~ua to carry out that
method, l~ needed to allow a CATV system to provlde dlfferent numbers of
~h~n~]~ to ~fprent subscribers, and at the same tlme retain the
abLlity to provlde up to all of thelr channels to up to all of thelr
subscribers. It is even more desirable for a CATV system to be able to
easily change the number of channels it is providing to any, of its
subscribers, at any time, and from time to time. mat is generally
deslrable becan~e most CATV systems charge different ; -~It~ to their
varlous subscribers, ~pRn~lng on how many of the supplied ch~nnPl~ the
partlcular subscriber wants to receive, and those features allow a
subscriber to easily change the number of ch~nnPlS he receives. The
result is that with those features a CATV system can easily sell
additional chAnnPl~ to its subscribers, or stop sen~ing chAnnPls to
sub~cribers who do not want them or are not paylng for them.
- Scrambllng and de-scrambling systems have been developed and are

1 used by some CATV systems to control whlch ch~nnel~ a particular
subgcrlber recelves. Certain channels are scramble~ prior to
transmission from the supplier's head end, and suh~e~l~ntly de-scL ~led
at the home ends of those subscribers who have paid for those scrambled
channels. A device commonly referred to as a de-s~L ll~r is installed
ln the paying subscribers homes, which restores the scrambled television
signal. Those ~ystems require acce~s to the subscriber's home, and man
power to do the lnstallatlon, or to remove the de-scrambler in the event
the subscriber no longer wants lt, or has stopped paylng the fee. Those
systems al~o run the rlsk of channels being pirated by subscribers who
have bullt, or purchased, thelr own lllegal de-scrambler.
Another known means of controlllng subscrlber access to the total
channels ln a CATV system is to selectively jam the channels to be denied
to the subscribers who have not paid for them. The ~ammlng of chamlels
ls usually accompllshed by s~n~lng a separate jammlng signal for each of
the channels to be ~ammed, together with the television slgnals, to the
subscrlber(s) for whom those chAnn~l~ are to be ~ammed. Each ~amming
slgnal can be a slgnal having a repetition rate close to the repetition
rate of the vertiQ 1 synchronization signal of the chAnn~l to be jammed,
and of a qreater amplltude. me television will pick up the ~amming
slgnal as the synchronizatlon signal and wlll therefore produce a
vertically unstAble picture. Similarily, the jammlng signal can be a
signal having a repetition rate close to the repetitlon rate of the
horlzontal synchronizatlon slgnal of the channel to be ~ammed, and of a
greater amplltude. The televlslon wlll then plck up the ~am~lng slgnal
as the horlzontal synchronl_atlon signal and wlll therefore produce a
hor17QntAlly unstable plcture.
A devlce ls requlred that wlll not only produce the requlred ~ammlng
signals, but also, wlll only combine the ~amming signals wlth the

~ ~ r ~
televlslon channel slgnals going to the subscrlber(s) who have not pald
for those channel.
some of the earlier prior art has used one separate line per
subscriber, and one RF switch per subscriber, per channel that might be
jammed. The separate subscriber lines are each coupled to a different RF
swltch for each channel that might be jammed, thereby creating a switch
and subscrlber line matrix in which each subscriber line has a unique RF
swltch for each channel that might be ~ammed, controlling that
subscrlber'~ acce~s to said ch~nnel, and ln which all RF swltches
controlling subscrlber access to a partlcular channel are connected to
each other. For example only, lf the situation is that channel "C" is to
be ~ammed to subscrlbers "101", "222", and "223", each of the channel "C"
RF swltches that couple the ~nq signal to those subscriber lines must
be closed. Accordlngly, lf there are 2500 subscrlbers and 4 channels to
be ~a~ned, 2500 ~ep~ le subscrlber llne~ are needed, and (4 x 2500) =
10,000 RF swltches are required. Accordingly, a large number of RF
swltches are required. In ~uch a system it would be difficult to add
further subscriber llnes and switches to the switch and subscriber line
matrix.
Some of the more recent prior art use d~LJdLd~ eS that are capable
of generatlng up to a flxed number of different ~ammlng slgnals, (for
example the maximum mlght be 6) sometimes contlnuously, and sometlmes on
a time divlslonal basls. In some of the more sophlsticated present art
sy~tems the ~ammlng signals are added on a tlme shared bases to the
subscrlbers llnes who are not permitted to vlew the particular channel
belng ~ammed. In many of the more sophlstlcated prior art systems that
add ~ammlng slgnal~ to subscrlber llnes on a tlme dlvl~lonal basls the
maximum number of ~amming slgnals that can be g~lleLd~ed ls eight or less.
Therefore, the maximum number of channels that can be ~ammed ls eight or
-- 3

~ ~ t~
1 less. That is obviously a problem for a CATV sy~tem that wants to offer
nine or more alternatlve ch~P~.
A number of dlfflcultles have to be overcome when jammlng slgnals
are not continuously added to the appropriate subscriber lines. However,
the benefits of addlng ~ammlng slgnals to the appropriate subscriber
1lnes on a time dlvlslona1 basls are great. Therefore it ls worth the
effort of trylng to overcome the dlfflcultles lnvolved ln time dlvlsiona1
~amming. A ma~or beneflt to tlme dlvisional jamming 1~ that only one
llne can be used to carry all of the different ~ammlng signals to one
subscriber. Only one 11ne has to be used, because when the ~ lng
slgnal belng transmltted is to ~am a channel the subscriber is not
entltled to recelve, then the RF switch to that subscriber's single
~amming signal line is closed, hence the subscriber recelves the jamming
slgnal, and that channel is ~ammed on the subscriber's television set.
However, when the ~amming signal be$ng transmltted is to ~am a channel
the subscriber ls entitled ~o receive, then the RF swltch to that
subscrlber's single ~ammlng signal llne ls left open, hence the
subscrlber does not recelves the ~ 1ng slgna1, and that channel ls not
~ammed on the subscrlber's teleY1slon set. The resu1t ls that the
channel ls ~ammed during the time lts ~ammlng slgna1 ls belng
transmltted, but not during the tlme lt's ~ammlng slgnal ls not belng
transmitted. Therefore, if the time between transmissions of the same
~ammlng slgnal ls to great, the channel wl11 only be ~ammed sometlmes,
hence it would be partly vlewable. It should therefore be a goal of time
dlvlslonal ~ammlng systems to reduce the time between ~r~ 5l0n5 of
the same ~amming slgnal so that the ch~nn~ ls humanly unviewable.
It ls more deslrable to produce a horlzontally unstable plcture than
a vertically unstab1e picture, as the former is more dlfficu1t to watch.
To produce a horl~Qnt~l1y unstable plcture the ~ammlng slgnal must ~e
-- 4

1 sent to each subscrlber who is to be ~ammed by lt ~nany thou~an~s of tlme~
per second, thereby effectively always jamming the television signal. To
accomplish transmitting different jamming signals on the same line many
th~ An~ of times per second, rapid switching is reguired; rapid or
contlnuous generatlon of the ~amming slgnals is also required, and
finally, the rapid switching and the j ing signals must be combined
correctly to the appropriate subscrlbers. Those skilled in the art will
percelve many problems in rapidly switching between frequencies and
malntalnlng acc~r~cy of frequency w1thln a small range.
Some of the more sophisticated prior art systems have used fixed
lnductlve circults whlch are alternately coupled with an osclllator to
generate different frequencies through that oscillator. Some of the
other more sophlsticated prior art systems have used a voltage controlled
oscillator to y~Jlerate the different ~amming frequencies on a time
divlslonal basls. T~he goals ln the prlor art have ~PnPr~1ly been to
effectlvely ~am the largest number of ch~nnPl~ wlth the least amount of
expenslve ~c ~ s, while at the same time allowing for control of what
ch~nnP~ are ~ammed to whlch subscrlbers, from the head end, with a
mlnlmum of e~ r-t ~ nrtlon. The goals of the present lnvention are
the same as the stated ~nPr~lly ~ epled goals in the prior art. The
pre~ent lnventlon accompllshes those goals in a new and efiective way not
contemplated by the prlor art, and for a greater number of channels than
the prlor art inventlons of which the Inventors of the present invention
are aware.
S o ary of the Inventlon
The invention teaches a method for controlling the reception quallty
of individual subscribers to CATV, and is comprised of the following

l ~teps. Flrst, selectlng and generatlng a Reference Frequency (~RFzn) for
each o~ the channels ~z~ to be ~ammed, wherein each RFz 15 a sultable
frequency for ~amming channel z. Second, sending an initial Freguency
Gen~ratlon Slgnal (~FGSa") to a generat~ng means, which causes the
generating means to generate a Jam~ing Freguency (nJFa") that is similar
to the carrler wave frequency of a typical television channel's signal,
and of a ~lightly greater amplltude. Third, comparing JFa to RFz, and if
JFa ls higher or lower than RFz, sen~lng a different FGSa, which is
elther lower ln voltage or higher in voltage, respectively, than the
prevlous FGSa, by an initial amount, to the generatlng means, causing it
to generate a new JFà. Then again comparlng the generated JFa with RFz,
and lf JFa ls hlgher or lower than RFz, sendlng a new FGSa, which ls
either lower in voltage or higher in voltage, respectlvely, than the
prevlous FGSa~ by less than the previous amount, to the generating means,
Qusing it to y~ne~ate a new JFa, which is again compared to RFz, until
the last increase or decrease in the voltage of FGSa resulted ln a
frequenc~ change in JFa of < I, {where "I" is a frequency value such that
RFz ~ I would ~am the televislon slgnal for whlch RFz i~ a IeL~ence
fLe~uenc~, lf the amplltude of RFz + I was withln the correct
parameters}. Fourth, ~torlng the last FGSa, as FGSz, where FGSz is the
FGSa that cause~ the generatlng means to generate a JFa that wlll jam
channel z. The JFa that will ~am chAnn~l z is called JFz. Fifth,
continuing the second, third and fourth steps untll there ls a stored
FGSz for each channel z, and then su~pen~1ng the second, third and fourth
steps. Slxth, ln contlnuous rotation, each for durations sultable for
~ammlng the horizontal synchronizatlon signal, c 'ln1n~ JFz with the
televi~ion ch~nn~lR signals being transmitted to subscr1bers who are not
entitled to recelve the telev1slon signal whlch JFz is ~ammlng. Seventh,
gll~pRn~lng the ~lxth step for a perlod long enough for the second, third,

1 fourth and fifth steps to be repeated, and then resuming the sixth step.
A preferred method of determlnlng the correct FGSz values ls to
reduce or increase the JFa by half of the preveious amount lt was reduced
or increased by, (l.e. uslng a blnary convergence method) untll the
change in JFa ls less than I. It is also preferred to store a FGSa, as
the FGSz, that resulted in JFa > RFz. Therefore it is preferred to
contlnue the comparision of JFa to RFz until: (a3 the last increase or
decrease in JFa was < I, and (b) the second last increase or decrease in
the JFa was < I, and (c) the second last increase or decrease in the JFa
was the opposite of the last lncrease or decrease in JFa, and then to
~tore as FGSz, whichever of the last and second last FGSa's resulted ln
JFa > RFz.
To accomplish the more desirable determination of the FGSz values,
and the more desirable FGSz values the follow'ng third and fourth steps
would replace the previously stated thlrd and fourth step~. New Third
Step, comparing JFa to RFz, and if JFa is higher or lower than RFz,
s~n~ln~ a different FGSa, which i5 either lower in voltage or higher in
voltage, respect'vely, than the previous FGSa, by an initial amount, to
the generating means, causlng it to y~nerd~e a new JFa. Then again
comparing the generated JFa with RFz, and if JFa is higher or lower than
RFz, sen~ a new FGSa, which is either lower in voltage or higher in
voltage, respectively, than the previou~ FGSa, by hdlf of the previous
amount, to the generating means, causlng lt to ~ene~dte a new JFa, which
is agaln c ~-ed to RFz, until: (a) the last increase or decrease in the
voltage o~ FGSa resulted ln a f eyuel~y change in JFa of < I, {where ~I~
ls a frequency value such that RFz ~ I would ~am the television slgnal
for whlch RFz is a reference freguency, if the amplitude of RFz + I was
wlthln the correct pdrameters} and (b) the second last increase or
decrease in the voltage of FGSa resulted in a frequency change in JFz of
-- 7 --

2~7~18~
l < I, and (c) the second last increase or decrease ln the voltage of FGSa
was the opposite of the last increase or decrease in FGSa. New Fourth
step, storing whichever of the last and second last FGSa's resulted in
JFa > RFz, as FGSz, where FGSz is the FGSa that causes the generating
means to generate a JFa that will ~am channel z. me JFa that will ~am
channel z 1s called JFz.
The method taught by the lnventlon also allows the ame ~ammlng
signal to be used to ~am both the horlzontal and the vertlcal
s~.~luon~latlon slgnals of the ch~nnPl~ to be ~ammed. To accomplish
~ammlng both the horizontal and the vertical synchronlzation signals, of
the chdnnels to be ~ammed, the Sixth Step is divlded into two steps, Six
(a) and Six (b). Step Six (a) ls 1dentical to the old slxth step. In
gtep Slx (b), in continuous rotatlon, each for durations suitable for
~ammlng the vertlcal synchronizatlon slgnal, each of the JFz's is
combined with the televi~ion channels signals being transmitted to
subscrlbers who are not entitled to receive the television signal which
JFz ls ~ammlng. Steps Slx (a) and S1x (b) are carrled out, on a time
shared basls, as determlned by the method oeerator, ln the perlod of time
durlng whlch the old S1xth Step would have been carrled out. The other
steps of the method are performed exactly the same whether there i5 only
a S1xth Step, or whether there 1g a Step Six (a) and a Step S1x (b).
The lnventlon, in addltlon to the stated method, also teaches an
apparatus for controlling the reception quality o$ individual subscrlbers
to QTV, whlch ap~d~d~u~ 1s comprised of the following c ~-n~nts. A
Voltage Controlled O~clll~tor ~VCO~) for generatlng a frequency (nJFan)
that ls slmllar to the frequency of a typical televis10n signal's carrier
wave frequency, and havlng a duration similar to a typical horlzontal
synchronlzatlon signal's duration, and of a slightly greater amplltude.
A ~et of subscriber Jamming Signal switches, each of which recelves the
-- 8

- ~ ~ 7 ~
1 JFa, and each of which will transmit the JFa to the llne of the
televlslon set of the sub~crlber to whlch lt ls connected. A Reference
Freguency Generat~ng ~eans that generates a reference freguency (nRJFz")
whlch ls suitable for ~amming channel z. A Comparlson ~ean~ that
S receives the JFa and that receives the RJFz, and can divide the JFa by a
factor of "D", where D is a factor such that if JFa is the correct
frequency to jam channel z, then JFa/D = RJFz, and which comparison
means can compare the RJFz to JFa/D and determine lf RJFz is greater than
or less than JFa/D. A servlce control center (nSCC~) that recelves
lnformatlon from the head end on which subscrlbers are entitled to
recelve whlch televlslon slgnals. Additlonally, the SCC outputs a
Frequency Generatlng Slgna7 (~FGSan) to the VCO, that determlnes the
frequency of JFa. Additionally, the SCC, based on the informatlon it
recelves from the head end as to the frequencies of the channels to be
~ammed, determine~ the value of D that the Comparison Means must dlvide
JFa by. Additionally, the SCC sends the information of what value D
should be to the Comparison Means, at the appropriate time.
Additionally, to start the system the SCC begins step ~Test~ by sending a
FGSa to the VCO, causing the VCO to generate JFa; then the SCC sends the
appropriate information on the value of D, so that RJFz x D would be the
appropriate frequency for ~amming channel z, to the Comparlson Mean
~he comparlson Means sends a first signal to the SCC lf the comparison
resulted in JFa/D > RJFz, and a second signal to the SCC if the
comparison resulted in JFa/D < RJFz; if JFa is higher or lower than RJFz
x D, then the SCC sends a dlfferent FGSa, which is elther lower ln
voltage or higher in voltage, r~yec~ively~ than the previous FGSa, by an
lnltlal amount, to the VCO, causing it to generate a dlfferent JFa.
Then, when the SCC recelves the result of the new comparlson from the
Comparlson Means, if JFa ls hlgher or lower than RJFz, the SCC sends a
.-- g

1 dlfferent FGSa, whlch ls elther lower in voltage or higher ln voltage,
respectlvely, than the previous FGSa, by less than the previous increase
or decrease, to the VCo. The SCC again receives the results of the
comparison of JFa/D to RJFz, and the SCC continues to receive the results
of the comparison and to send out different FGSa's which are either
increased or reduced by less than the increase or decrease of the
previous FGSa was, until the last increase or decrease in the frequency
of JFa was < I, {where ~H is a pre-det~rrln~d~ fixed, frequency value
such that (RJFz x D) + I is close enough to RJFZ x D, to jam the
televislon slgnal of chAnn~1 z if it's amplitude were high enough}, the
SOC then stores the last FGSa, as FGSz, where FGSz is the FGSa that
causes the generatlng mean~ to generate a JFa that wlll ~am channel z.
The JFa that wlll ~am chAnn~l z is called JFz. Additionally, the SCC
contLnues to operate as stated until there is a stored FGSz for each of
the chAnnel~ to be ~ammed. Once all of the FGSz's have been stored step
Test is ended. Additionally, the SCC then Sn~pen~ the operations of
step Test and begins ~tep Jam by, where N ls the number of telèvlsion
slgnals being ~ammed, ~n~1ng~ in cont1nuoll~ rotation, each for durations
suitable for ~ammlng the horizontal synchronization signal, each of the
FGSZ'S to the VCO, and closlng each of the Subscriber Jamming Signal
Swltches to the subscribers who are not entitled to receive the
televlsion slgnal of chAnn~l z, when FGSz is being sent to the VCO~ and
openlng the Jammlng Slgnal Switches of those subscribers who are entltled
to recelve channel z, when FGSz ls belng sent to the VCo. Addltionally,
after a pre-determ1ned perlod of time the SCC suspends step Jam for a
period of time long enough for step Te~t to be perr~ -~, and again
performs step Test, and then again sl~p~n~ step Test and again resumes
step Jam, and contlnues to do so at the pre-determ1n~d perlods of tlme.
The appa~dtus taught by the inventlon also allows the same ~ammlng
-- 10

1 slgnal to be used to ~am both the horlzontal and the vertlcal
synchronzlatlon ~lgnals of the channels to be ~ammed. To accompllsh
~ammlng both the horlzontal and the vertlcal synchronizatlon slgnals, of
the channels to be ~ammed, the SCC performs step Jam as follows: the SCC
send~, in contlnuous rotation, each for duratlons suitable for ~ammlng
the horlzontal synchronlzation signal, each of the FGSz's to the VCo, the
SCC also, ln contlnuous rotation, on a time shared b~sis, as determlned
by the system operator, also sends, each for duratlons suitable fo~
~ammlng the vertical synchronization signal, each of the FGSz's to the
VCO, and the SoC causes the closing of each of the Subscriber Jamming
Signal Switches to the subscrlbers who are not entltled to recelve the
televlsion slgnal of channel z, when FGSz is being sent to the VCo, and
causes the openlng of the Jamming Signal Switches of the subscribers who
are entitled to receive ch~nn~l z, when FGSz is belng sent to the VCo.
A preferred method of determlnlng the correct FGSz values, ln an
a~yaLa~u~ of the invent~on, ls to reduce or lncrease the JFa by half of
the preveious amount it was re~ced or lncreased by, (i.e. using a binary
con~ nc~ method) until the change in JFa is less than I. It is also
preferred to st~re a FGSa, as the FGSz, that resulted in JFa > RFz.
merefore in a more prefeLLed ~y~L~Lus, the SCC would PeL~ the
followlng Step Test; the SCC beglns step ~Te~t~ by sending a FGSa to the
VCO, causlng the VCO to generate JFa; then the SOC sends the appropriate
lnformation on the value of D, so that RJFz x D would be the appropriate
frequency for ~ammlng channel z, to the Comparlson Means. The Comparlson
Means sends a first slgnal to the SCC if the comparison resulted in JFa/D
> RJFz, and a second signal to the SCC if the comparison resulted in
JFa/D < RJFz; if JFa is hlgher or lower than RJFz x D, then the SCC
sends a dlfferent FGSa, whlch ls elther lower in voltage or hlgher ln
voltage, re~pectively, than the previous FGSa, by an initial amount, to

~7~
1 the VCO, causing lt to generate a dlfferent JFa. Then, when the SCC
receives the result of the new comparison from the Comparison Means, if
JFa is hlgher or lower than RJFz, the SCC sends a different FGSa, which
is elther lower in voltage or hlgher in voltage, respectively, than the
previous FGSa, by half of the previous lncrease or decrease, to the VCo.
The SCC agaln recelves the results of the comparlson of JFa/D to RJFz,
and the SCC contlnues to recelve the results of the comparl~on and to
send out dlfferent FGSa's whlch are elther lncreased or Ledu~-~d by half
of what the lncrea~e or decrease of the prevlous FGSa was, untll: (a) the
last increase or decrease in the frequency of JFa was < I, {where "I"
ls a pre-determ1n~d~ fixed, frequency value such that tRJFZ x D~ ~ I is
close enough to RJFz x D, to jam the television signal of channel z if
lt's amplltude were hlgh enough}, and ~b) the second last lncrease or
decLease ln the frequency of JFa was < I, and tc) the second last
increase or decrease in the frequency of JFa was the opposite of the last
lncrease or decrease in JFa. Addltionally, the SCC then stores whichever
of the last and second la~t FGSa's resulted ln JFa/D > RJFZ, a8 FGSZ,
where FGSz ls the FGSa that Quses the qeneratlng means to generate a JFa
that wlll ~am channel z. The JFa that wlll ~am channel z ls Q lled JF~.
Addltlonally, the SCC cont1m ~ to operate as ~tated untll there ls a
stored FGSz for each of the channels to be ~ammed. Once all of the
FGSz'~ have been stored step Test ls ended.
Step Test has two functions. Firstly, it allows the SCC to
determlne all of the FGSz values, and store them, so that the SCC ls
able to Quse the approprlate ~amming frequencies to be generated at the
approprlate tlmes. The second purpose of step Test, ls that lt allows
the SCC to period1c~lly re-determlne all of the correct FGSz values.
Temperature, humldity, and other variables can result in dlfferent
fLe~u~n~ being ~neLdted from the same FGSz values, after a perlod of

1 tlme. Therefore " t l~ necessary to perlodlc.~lly re-Q lculate the FGS~values, as after a period of t1me those values mdy hdve to be changed,
because what was at one time causing a correct ~amming fre~uency to be
generated, at another time could be causing an incorrect ~amming
S freguency to be generated. By periodically performing step Test, the SCC
periodically correctly r~lc~ tes and stores FGSz values, which are
correct at the time they are c~lc~llated, and should remaln correct
approximately until step Test is again performed, if the correct time
perlods have been chosen by the system operator.
Some of the ad~an~ay~s of the method and a~yaLdLu~ taught by the
invention are that a very effective ~amming of each of the channels to be
~ammed is achieved, and that only one ~amming signal switch may be
re~ulred per subscriber. Another advantage is th~t access to the
subscriber's home is not needed to allow the subscriber to receive
channels that are ~ammed, and access to the subscriber's home is not
needed to deny the subscriber access to ch~nnpl~ that are being ~ammed.
Anothèr advantage is that addltional subscribers can easily be added to
the system as each subscriber need only be connected to the system by
one subscriber csn~ctlon and one ~amming slgnal swltch, accordingly, to
add on an additlonal subscriber all that may be needed ls to add on to
the end of a linear series of subscrlber connectlons and ~amming slgnal
switches, one addltional subscrlber conn~cllon and one additional ~ammlng
signal swltch. Another ad~antage to the lnventlon ls that which channels
any subscriber receives can be pro~ into the system from the head-
end, wlth no nèed to touch the subscrlber's recelver end. Another
advantage is that the method of the invention, and an a~a~a~ua built
~c~rdln~ to the method of the lnvention can ~am up to twelve channels.
Another advantage is that which of the channP~ are jammed can be
determined at the head-end. The operator merely has to decide which
- 1 3

g ~
1 channels are to be ~ammed, withln a certaln range, and the SCC deter~n~s
what the values of D shou1d be. Therefore, if at one tlme the ~y~tem ls
~amming channels 7, 8, 9, 10, 12, 15, 16, 18, 19, 20, 21, and 22, and
then at a later tlme lt is desired that the system should not jam
channels 12 and 21, that Q n be programmed lnto the system from the head-
end, with no need to touch the receiver ends. If at another time it is
desired to no longer ~am channels 10, 16, and 20, but to begin ~amming
chAnn~-~ 13, 14, and 17, that can be programmed lnto the system from the
head-end wlth no need to touch the recelver ends, and so on. Another
advantage to the lnvention ls that it allows the same ~amming signal to
be used to alternately ~am the horizontal and vertical synchronlzatlon
slgna1~, thereby allowlnq for a very effectlve ~ammlng, as not ~ust one
but both synchronlzatlon slgnals are belng ~al~med.
Brlef Descrlptlon of the Drawlngs
Flgure 1 ls a s. tlc dla~ showlng a preferred embodlment of an
ap~Ldtu~ of the lnventlon;
Flgure lA ls a schematlc dlag showlng a preferred ~ '~o~ t of an
ap~ us of the inventlon working ln conjunction with a
control means and TV slgnal swltches;
Flgure 2 ls an illustratlon showing the ~requency spectrum of a
televlslon signal and lndlcating where the ~ammlng signal of
the lnventlon would fall wlthln that freguency spectrum;
Flgure 3 ls a tlmlng dta-, lllustratlng one po~slble tlmlng scheme for
the horlzontal ~ammlng pu1se of the inventlon when lt has been
set up to ~am a total of twelve channels, and to ~am channels
1, 4, and 9 to subscrlber "X";
Flgure 4 ls a tlmlng dlagram lllustratlng one po~slble tlmlng scheme for

2~7~89
1 the vertlcal ~amming pulse o~ the invention when lt ha~ been
~et up to ~am the same twelve channel~ a~ ln flgure 3, and to
~am the same channels 1, 4, and 9 to subscrlber "X", as in
flgure 3;
Flgure 5A i~ a schematic diagram of the master switch of the preferred
~ nt of an apparatus according to the present inventLon;
Flgure 5B is a schematic diagram showing the eguivalent R.F. circuit of
the master swltch lllu~Lated in Figure 4A, when that master
swltch ls on;
Figure 5C ls a ~chematic diagram showlng the equivalent R.F. circuit of
the master swltch lllustrated ln Figure 4A, when that master
swltch is off;
Figure 6 l~ a ~ch~ Llc ~1a- of the variable attenuator of the
preferred embodlment of an apparatus according to the pre~ent
inventlon.
Descrlption of thc P~Çc~c~ Embodiments
me preferred ~ of the method for controlllng the .
reception quality of individual subscribers to CATV, where each of the
~hA~n~ P~rally referred to a~ ch~n~l ~z~, are to be ~electively
~ammed to selected ~ubscrlbers, is comprised of the following steps.
Flrst, selectlng and generatlng a ~eference Freg~enc~ tnRJPZ~), such that
where D ls a number, RJFz x D would be a ~ammlng signal for channel z.
Second, se~tn~ an lnltial Fre~ enr~ Generat~on Signal (~FGSa~) to a
generatlng means, which causes the generatlng means to generate a ~a~nlng
frequency ~JFa~J that is slmilar ln frequency to the carrler wave
fre~uenc~ of a typlcal televlslon ch~nnel's signal, and of a duration
slmilar to that of a typical horizontal synchronizatlon signal's
- 1 5

~ t'~
1 duratlon, and of a slightly greater amplitude. Thlrd, dlviding JFa by D
and then co~paring JFa~ to R~F~, 3nd ~f ~T~ hiqh~r or lo~r t*~n
RJFz, sending a dlfferent FGSa, which is either lower in voltage or
higher in voltage, respectively, than the previous FGSa, by an initial
amount, to the generating means, cau31ng lt to generate a new JFa. Then
agaln comparlng the ~nerd~ed JFa/D wlth RJFz, and lf JFa/D ls hlgher or
lower than RJFz, ~en~1ng a new FGSa, whlch 1s elther lower ln voltage or
hlgher in voltage, respectlvely, than the prevlous FGSa, by half of the
prevlous amount, to the generatlng means, caus1ng lt to generate a new
JFa, which is agaln dlvlded by D and - ed to RJFz, until: ~a) the
last increase or decrease JFa was < I, {where "I" is a frequency value
such that tRJFz x D) + I would ~am the televlslon signal for which RJFz
ls a reference ~ammlng frequency, lf the amplltude of (RJFz x D) + I was
wlthin the correct E~ -ters}, and (b) the second last increase or
decrease ln the JFa was < I, and (c) the second last increa~e or decrease
ln the JFa was the opposite of the last increase or decrease ln JFa.
Fourth, storlng whichever of the last and second last FGSa's resulted in
JFa/D > RJFz, as FGSz. FGSz is the FGSa that causes the generatlng
means to generate a JFa that wlll ~am channel z. The JFa that will ~am
channel z Is called JFz. Fifth, contlnulng the second, thlrd and fourth
steps untll there ls a stored FGSz for each channel z, and then
suspending the second, thlrd and fourth steps. Slxth, where N 1s the
number of telev1s1On s1gnals belng ~ammed, ln contlnuous rotation, each
for duratlons of approxlmately 6 to lO ~S, comblnlng JFz with the
televlsion channels signal~ being transmitted to subscribers who are not
entltled to receive the television signal which JFz is ~amming. Seventh,
where N ls the number of ch~nnel~ belng ~ammed, ln contlnuous rotation,
once approxlmately every lS to 20 mS/N, each for duratlons of
approxlmately l~0 to 300 yS, çomblnlng JFz wlth the televlsion channels
- 1 6

7 ~
1 slgnals belng transmltte~ to subscrl~er~ who are not entltle~ to recelve
the televl~lon slgnal whlch JFz ls ~ammlng. Elghth, during step~ ~lx and
seven, varylng the amplltude of JFz approximately ten times per second by
up to 6 db. Ninth, suspending the sixth and seventh steps for a period
S long enough for the second, th~rd, fourth and fifth steps to be repeated,
and then resuming the sixth and seventh step.
The ~amming signal being transmitted for durations of between
approxlmately 6 ~n~ 10 ~S wlll ~am the horizontal synchronization signals
of channel z. That same ~ammlng slgnal, belng transmltted for duratlo~s
o~ approximately 150 to 300 ~S wlll ~am the vertical synchronization
slgnal of channel z. It therefore can be seen that the preferred
em~o~ t of the lnventlon uses the same ~amming slgnal frequency to, at
one point, ~am the horizontal synchronizatlon signal, by transmltting it
in burst lasting only 6 to 10 pS; and at another point, ~am the vertlcal
synchronlzatlon ~lgnal, by transmitting the JFz in bursts lastlng l~Q to
300 ~S.
ffl e advantage of varying the amplitude of the jamming signal,
contin~loll~ly, a number of tlmes eer second, is that ~t lmproves the
effectlveness of ~ ~n~ on all televislon sets. Some televislon sets
have nolse fllters that could potentially fllter out a ~ammlng signal of
a flxed amplltude, however, they would, ln most cases, not be able to
fllter out a ~ammlng slgnal o~ a varylng amplltude.
me ~LeL6~Led ~ ~ 1 ~ t of an apparatus accordlng to the lnventlon
ls lllustrated ln flgure 1. The TV slgnal 10, which ls received by the
pLeLe~Led ~ 1 t carrles all of the possible television chAnn~ the
preferred embodlment ls bullt to ~am, and may also carry addltional
television ch~nnel~. The yLe~eLred ~- c i - ~ is comprised of: a set of
television slgnal splltter clrcults 21; a set of ~ammlng signal swltches
23; a set of subscriber signal combiner modules 22; a voltage controlled
- 1 7

1 oscillator (UVW ~) 29; a Digital to Analog Converter (~DAC~) 25 18; a
Shlft Reglster (~SR~) 26; a Servlce Control Center ~NSCCn) 27; a Quartz
cryst-~l reference frequency generatlng means (~REF~) 2~; a Frequency
Comparator Circult I~FCC~) 29 ; an Integrator 30; a 8uffer 31; a master
~vitch 32; a variable attenuator 33; and a lov pass fllter 34.
In the preferred embodlment each of the television signal splitter
clrcuits 21 recelves the TV signal. The set of ~amming slgnal swltches
23 in the preferred ~ t is made up of M (where M is an integer)
PIN Dlodeg RF swltches. Each of the ~ammlng slgnal switches receives the
~ammlng slgnal. The set of subscrlber connections in the preferred
~ -l ls made up of M slgnal comblner ~ le~. In the preferred
e ~ t the slgnal comblner - l~ are constructed using splitter
clrcults. Each subscrlber conn~ctlon col~,ec~ the signa1 being put out
from that subscriber's televislon signal splitter clrcuit and the signal
belng put out by that subscrlber's ~amming signal switch. Accordingly,
when the subscriber's ~ammlng slgnal switch is closed whlchever channel
1~ belng ~ammed by the ~amming slgna1 will be ~ammed on that subscriber's
televlslon set.
The FCC ig a circ~it that receives two inputted frequencies, one
that is constant, and one that varles, lt divldes the variable inputted
freyuen~-~ by a det-- 1n~d factor, and then-compares the divlded lllpuL~ed
fre~enc~ to the c~ ~ant ir.~uL~ed frequency and determines which ls
greater. In the Preferred , ~ ---t the FCC also dlvlde~ the con- ~n~
lnputted fre~uen~y by a factor before making the compari~on, however,
~5 that ls not e~sentlal. It ls only nec~ ry that the FCC be able to
dlvlde the lnputted frequency that will vary, by dlfferent factors.
In the preferred ~- ~dl -n~ the REF puts out a frequency of 4 MHz,
wlthln 1 KHzr whlch 1~ dlvlded ln the FCC by 32 to provlde a constant
reLerence freyuency of 125 KHz. me constant reference frequency u~ed
- 1 8

1 does not have to be 125 ~Hz. Any sultable constant reference freguency
- could be used. The 3ultable ~eference freguen~y ~h~ch the FC~ use~ vlll
be called "R~Fn. It ls not essential that the REF ls a frequency that
resulted from an initlal frequency belng divlded by a factor before belng
used by the FCC for comparison. me REF could be a frequency that is
used directly by the FCC, ln which case it would not be necessary to have
the FCC dlvlde the REF by a factor before using lt.
me output of the FCC is pulsatory, and could be depicted as a
square wave whose duty cycle varies. The Integrator ls needed to avera~e
the pul~atory output of the FCC and send one of two continuous signals to
the SCC; whlch of the two signals lt sends depends on the result of
averaging the output of the FCC.
Figure 5A ls a schematlc diagram of the master swltch 32 of the
preferred embodiment, which lllustrates its con~,u~ion. The master
swltch ls a PIN dlodes RF lnterruptor that h~s a controlled rise and fall
time to mlnimlze the generation of spurious products during swltching.
me master swltch is made up of the following components: a grounded
capacltor connected with an inductor (which is called an "RF Choke"); six
addltlonal capacitors; five diodes; and four addltlonal inductors. A
flr3t capacltor, which is the input, is followed by a shunt RF Choke,
followed by a series first dlode, followed by a shunt second capacitor,
followed by a series second diode, followed by a serles flrst inductor,
followed by a shunt thlrd Q pacitor, followed by a series thlrd diode,
followed by a ~erie~ second ~ L~ followed by a shunt fourth
capacitor, followed by a series fourth dlode, followed by a series third
inductor, followed by a shunt flfth capacltor, followed by a series fifth
diode, followed by a shunt fourth inductor, followed by a series sixth
Q pacitor, whlch is the output. When the master swltch ls on, direct
current flows ~ou~h the dlodes and they become conductive; the master
-- 19

~7~ ~ ;3~
1 swltch ls then the equlvalent of a low pass filter havlng a cut-off
frequency hlgher than the highest frequency of interest, the schematlc
: dlagram of that equivalent clrcuit is lllustrated in figure 5B. When the
master switch ls off the current stops flowing through the PIN diodes and
S then each dlode becomes llke a small capacltor; the master swltch is then
the equlvalent o~ a capacltlve ladder attenuator, which equlvalent
clrcult ls lllus~Lated in flgure 5C.
me Varlable Attenuator of the preferred ~ t ls lllustrated
ln flgure 6. It has two puL~oses, firstly lt is used, when nec~s~lry~ to
ad~ust the ~mplltude of JFz to a level slightly higher than the amplitude
of the signal lt is ~ammlng, secor~ly, lt ls used to, on instructlon from
the SCC, cont1m1o11~ly make small ch~nqe-~ to the amplitude of JFz at the
rate of approxlmately 10 Hz. The Varlable Attenuator ls made up of the
following c ~ c-ts: a grounded capacitor, followed by three resistors,
six additional capacltors, three addltional resistors, and three
a~el,ua~or type pln dlodes. It can be seen from figure 6 that the
Varlable A~tenl~tor circuit used ln the preferred ~ t ls made up
of a flrst capacltor, ~ollowed by a shunt reslstor and a reslstor and
capacltor ln E~r~llel/ but ln serles wlth the.signal, followed by a shunt
d~ode, followed by a co~ n~ capacltor, followed by a shunt reslstor and
a reslstor and capacltor ln ~r~llel, but ln serles wlth the slgnal,
followed by a shunt dlode, followed by a coupling capacitor, followed by
a serles reslstor, followed by a shunt diode that is in series wlth a
coup11n1 capacltor. ffle SCC of the preferred . ~ t sends a voltage
~5 that wlll dynamlcally modify the resistance of the pin diode of the
Varlable Attenuator, thus giving it continuous range.
The low pass fllter 39 of the preferred embodiment ls made up of
capacltors and ln~u~-oLs. me purpose of the fllter ls to elir1n~te the
harmonlcs from the osclllator and master switch clrcult.
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1 The buffer -~1 prevents feedback from gettlng to the output end of the VCO when the ma~ter ~wltch swltche~ on or off.
The servlce control center 27 ls an electronic control unit. The
servlce control center of the preferred embodiment is made up of a
microcontroller with a ROM program, RAM circuits, logic I.C.'s,
operational amplifler~ and the n~c~ ry assorted inputs, outputs and
~dndard clrcultry necessAry for operatlon. The service control center,
when lt first starts operating lnltlallzes the system by closing the
maRter ~witch and openlng all ~wltche~ ln the ~et of ~ammlng ~lgnal
swltches 23. The SCC then beglns step "Test" by outputtlng a digltal
code that represents a ~lgnal (~DCSaN) to the SR 26, whlch the SR output~
to the DAC 25, whlch converts lt lnto an analog voltage which we will
call the frequency generatlng ~Ignal ~nPGSa~) which lt sends to the VCO.
The FGSa determlnes the frequency whlch ls outputted by the VCO, whlch
frequency ls referred to as "JPa~. The SCC a1so, based on the
lnformatlon lt recelves from the head end as to the frequen~ of the
channelg to be ~ammedj determines, for each channel "~ to be ~ammed, the
value of D that the FCC must divide JFa by, so that if JFa/D = h~, then
JFa w111 ~am channel z. me SCC sends the information of what value D
should be to the FCC, at the appropriate tlme. The FCC also receives the
JFa from the ~uffer 31. The FCC compares JFa/D to REF and sends the
result to the Integrator, whlch sends a flrst signal to the SCC if the
comparlson resulted ln JFa/D > ~, and a second signal to the SCC if
the comparison resulted in JFa/D < REF; lf JFa/D ls hlgher or lower than
~5 R$F, then the SCC sends a dlfferent DCSa, whlch wl11 result in a JFa that
ls either lower ln f~e~uell~y or higher in fre~en~y, respectlvely, than
the prevlous JFa, by an lnltla1 amount. Then, when the SCC receives the
result of the new comparlson from the Tnte~rator, if JFa/D is hlgher or
lower than h~, the SCC sends a d1fferent DCSa, whlch will result in a
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2 ~
1 JFa that ls elther lower ln frequency or higher in frequency,
respectively, than the previous JFa, by half of the previous increase or
decrease. The SCC agaln recelves the results of the comparlson of JFa/D
to REF, and the scc continues to receive the results of the comparison
and to ~end out different DCSa's, which will result in JFa's that are
elther lncreased or reduced ~y half of what the increase or decrease of
the prevlous JFa was, untll: (a) the la~t lncrease or decrease in the
freguency of JFa was < I, {where ~l~ is a frequency value such that JFa +
I would ~am the same televlsion slgnal that JFa would ~am}, and ~b) the
second last lncrease or decrea~e in the fre~ ry of JFa was < I, and (c)
the second last increase or decrease ln the frequency of JFa was the
oppo~lte of the last lncrease or decrease ln JFa. Additlonally, the SCC
then ~tores wh~chever of the last and second last DCSa's resulted ln
JFa/D > REF, as DCSz. DCSz is, of course, the DCSz that results ln the
VCO ~nerdLing a JFa that wlll ~am chAnnel z. The JFa that wlll ~am
channel z ls called JFz. The SCC contlnues to operate as stated untll
there ls a stored DCSz for each of the ch~nn~l~ to be ~ammed. Once all
of the DCSz's have been stored step Test l~ ended. The SCC then s ~y~
the operatlons of step Test and beglns step Jan by, sen~1ng~ ln
contlnuous rotatlon, each for duratlons of approxlmately 6 to 10 ~S, each
of the DCSz's to the voo, and closlng each of the Subscrlber Jammlng
Slgnal Switches to the subscrlbers who are not entitled to recelve the
televlslon slgnal of channel z, when DCSz ls belng sent to the VCO, and
openlng the Jammlng Slgnal Swltches of those sub~crlbers who are entltled
to recelve channel z, when W z ls belng sent to the voo. The SCC also,
during step Jam, sends, approxlmately once every 1.2 to 1.7 mS, in
contlnuous rotatlon, 0.15 to 0.30 ~S long pulses of each of the DCSz's to
the VCD, and closes each of the Subscriber Jammlng Slgnal Swltches to the
subscrlbers who are not entltled to recelve the televlslon slgnal of
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-- 2 ~
1 channel z, when DCSz ls being sent to the VC4, and opens the Jammlng
Slgnal Swltches of those subscrlber~ who are entlt1ed to reGelve channel
z, when DCSz ls belng sent to the VCO. The SCC, also durlng step Jam,
ln~ru~ the Varlable Attenuator to vary the amplitude of JFz
approxlmately ten tlmes per second, by up to approximately 6 db. The SCC
a1so, durlng step Jam, v~ries the dlgltal code it sends out as DCSz, so
that the frequency of JFz varies slightly ~preferably wlthin a range of 0
to 800 KHz). me SOC a1so, after a pre~det~rrln~d perlod of tlme ~1
stlqpe~ step Jam for a perlod of tlme T2, whlch ls long enough for ~tep
Te~t to be performed, and the SO~ agaln performs stee Test, and then the
SOC agaln ~u~ends step Test for a period of tlme Tl, and agaln resumes
step Jam for perlod T2, and contlnues to alternate between step~ Test and
Jam, during perlods T2 and T1, reseectively.
In the preferred embodiment period T1 varies from 5 minutes up to
1~_ Mlnutes when the system is warmlng up, and T1 = approxlmately 60
Minutes after the s~stem has reached lts operatlng t- ~rature. In the
~L~L~rLed e~bodlment period T2 = approximately 1 second. me lengths of
tlme of perlods Tl and T2 can, of course, be varied without alterlng the
te~h1n~ of the lnventlon.
Flgure 2 lllu~ates a typlcal televlsion slgnal frequency spectrum,
and where the ~amming signal of the invention would appear. The ~amming
slgnal of the lnventlon has an amplltude greater than that of the
synchronlzatlon signal.
The televlslon sets of the subscribers who have had a jamming signal
added to thelr televlsion slgnals, lf tuned to the jammed channel, will
therefore lock onto the ~amming signal (since it is of a greater
amplltude) lnstead of the proper horlzontal synchronlzatlon signal,
durlng the ~ to 10 ~S pu1ses, and will have a horizontally w table
plcture. Durlng the 0.15 to 0.30 ~5 pulses the televlslon sets tuned to
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207618~
l the ~ammed channel will lock onto the jamming slgnal lnstead of the
proper vertical synchronization ~lgnal, and will have a vertically
unstable picture. me preferred ~ r--~t ~am~ both the horlzontal
synchronizatlon slgnal and the vertical synchroni2ation signal of every
ch_nnel to be ~ammed, to the appropriate subscrlbers, many times every
second. The preferred embodlment therefore achieves a much more
effect~ve ~_mmlng than any of the prlor art ~- ~llr~nts which only ~ammed
elther the vertlcal synchronization ~ignal or the horizontal
~ynchronlzatlon signal, but not both.
In the ~,efe~Led ~---'o~ t a very effective ~amming of each of the
channels to be ~ammed is achieved, and only one ~ammlng slgnal switch i
requlred per subscriber. Additional advantage~ to the preferred
embodiment are also a~arent. Access to the ~ubscrlber's home 15 not
needed to allow the sub~criber to receive ~hAnn~l~ that are ~ammed, and
access to the ~ubscrlber's home is not needed to deny the subscrlber
access to chAnn~l~ that are belng ~ammed. Suh~crlbers can easily be
added to the system as each subscrlber need only be conn~cted to the
system by one sub~crlber connectlon and one ~ammlng signal switch,
accor~ 1y, to add on an additlonal subscrlber all that 14 be needed ls
to add on to the end of the linear ~erles of subscrlber connections and
~ammlng signal swltche~, one addltional ~ubscrlber connectlon and one
addltlonal ~amming slgnal swltch.
It is anticipated that generally the inventlon and especially the
ulef6~Led embodlment of an a~oua~u3 of the invention will be used ln
con~,ctlon with a control means and wlth TV signal swltches lnstead of
televl~lon slgnal splltter clrcults. Flgure lA lllu~L~dtes the inventlon
worklng ln coniunctlon wlth a control mean~ 35 and wlth TV ~lgnal
~wltches 36. In operatlon the TV ~lgnal, ha~ sent along wlth it, coded
lnformatlon that tell~ the control means whlch TV slgnal swltches 36
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l should be turned on, and whlch subscrlbers ~hould have whlch of thelr
channels ~ammed. The constructlon of a control means able to recelve
coded lnformatlon telling lt whlch TV signal swltches to turn on, and
which subscrlbers should have which of thelr chAnn~ ammed, and able to
tur~ on the approprLate TV slgnal swltches and able to lnform the SCC
which sub~c~lbers should have whlch of their ch~n~ ammed, is well
known ln the art. TV slgnal swltches i~ also well known ln the art. For
example only, they could be PIN Dlodes RF s~ltches or RF relay switches.
When the preferred ~ t of an apparatus of the lnventlon ls
used ln con~wlc~lon wlth a control means and wlth TV slgnal swltches lt
ls very slmple for a CATV operator to deny certaln channels to certaln
subscrlbers from the head end. m e CATV operator merely enters the
approprlate information into the system at the head end. The information
ls then transmitted along wlth the TV signal to the control means, which
~eco~e~ that lnformatlon and provldes lt to the SC~. The SCC then causes
the approprlate subscribers' ~ ~ng signal switches to close at the
appropriate tlmes and the approprlate ~amming signals are combined to
those subscribers received television slgnals, thus denylng them the
appropriate channels.
Varlatlons to the ~,ef~red ~ can easily be made. me
signal combiner modules could be col~ru~-~ed uslng dlrectional couplers
instead of splitter clrcults as ls used ln the preferred ~ t. The
swltches of the set of ~ammlng slgnal ~wltches, could for example only,
be RF Ga As Fet swltches lnstèad of PIN Dlodes RF swltches as are used in
the preferred ~ t. The master swltch, for example only, instead
of being con~LLuc~ed as described for the preferred P ~ t, could be
con~Lu~ed using a Ga As Fet RF switch assembly.
Additlonal variations to the preferred embodlment are also posslble,
the followlng are only a few addltional examples. The Quartz crystal
_ ~ 5

2~76~ ~
1 reference frequency generatlng means of the preferred embodlment ls
preferred because Quartz is very stable, and when a clrcult passes the
correct current through lt, lt will glve out a resonances fre~uency that
ls very stable and rellable under temperature and other changes.
S However, for ex~mple only, a coll and capacltor clrcult could be used to
replace lt, as could any type of device or circuit that will qenerate a
rellable frequency.
The InLegLdtor of the preferred embodlment is not essentlal to the
lnventlon. It ls only essentlal that the result obtained by the
comparlson perf. -~ by the FCC be c ~cated to the soc, any means of
communlcatlng that result to the SCC will allow the inventLon to
functlon. Slmilarlly, an SCc could output a voltage dlrectly to the vC
ellmlnatlng a need for a Shlft Register and a DAC. The preferred
; ~d1 - ~ employs a Shlft Reglster and a DAC to allow serial
transmlsslon of the 1nf~ -~lon from the SCC, instead of parallel
tran~mlsslon, whlch would requlre more output connectlons from the SCC.
The Varlable Attenv~tor ls also not essentlal to the funct~oning of
the lnventlon, as the invention could functlon without varying the
amplltude of JFz wlthln a range of workable amplltudes. However, the
lnventlon would not be as effective, on all television sets, if the
amplltude of JFz was not varled, however, lt would stlll be effective
enough to perform lts functlon.
Flnally, many alternatlve ways to COn~LLU~L the servlce control
center and ~ome of lts componentR wlll be clear to thoRe ~kllled ln the
art.
Accordlngly, many alternatlves to the con~Lru~Lion of the preferred
embodlment, som~ of whlch are obvlous to those skllled ln the art but not
speclflcally stated hereln, wlll be apparent to those ~ ed ln the art.
Th1g ~1RC1O~re ls therefore to be understood as lllustratlve of the
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2 ~
1 lnventlon and not as a llmltatlon of the lnventlon. All su~h
modification~ and alternatives which do not depart from the te~-h1ng~ of
thls lnventlon are lntended to be lncluded wlthin the claims.
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Representative Drawing